Radiation therapy is currently used to treat localized cancer. In a typical application, a radiation delivery system has an ionizing radiation device mounted to a movable gantry. The radiation delivery system controls the motion of the radiation device to direct an ionizing radiation beam to a specific point in space commonly referred to as the “machine isocenter.” One aspect of radiation therapy is positioning a patient so that the tumor is located at the machine isocenter. Calypso Medical Technologies, Inc. has developed systems and methods for accurately locating and tracking a target in a patient. The Calypso systems can provide objective information regarding the location of the tumor relative to the machine isocenter during patient setup procedures or while the ionizing radiation beam is irradiating the patient in real time (e.g., in less than 2 seconds from taking a measurement and in intervals of less than every 5 seconds).
One challenge of locating and tracking a tumor within a patient while the ionizing radiation beam is energized is that the tumor may move. Common sources of tumor movement during treatment include respiration, gastrointestinal functions, and muscular movement. The localizing and tracking systems developed by Calypso Medical Technologies, Inc. track the tumor or other target of the patient to ensure that the tumor is located at a desired position relative to the machine isocenter. The localizing and tracking system accordingly needs to provide accurate data to mitigate irradiating healthy tissue adjacent to the target.
One aspect of localizing a tumor is that conventional patient support systems for use in radiation therapy can impair the accuracy of the localization systems. Conventional patient support systems typically have a pedestal, a cantilevered support structure attached to the pedestal, and an insert carried by the cantilevered support structure. The insert generally includes a pass-through zone having a carbon fiber grid, and the cantilevered support structure generally has two beams that support the insert. The grid is designed to be compatible with the ionizing radiation beam and to provide sufficient support to sustain the load of the patient. Several different support systems and inserts are described in U.S. Pat. Nos. 5,778,047; 5,806,116; 5,537,454; and 6,161,237, all of which are herein incorporated by reference. Although the conventional patient support systems described in these patents are compatible with the ionizing radiation beams, they are not well suited for use with localizing and tracking systems that use magnetic fields or other types of signals to track the tumor.
Conventional patient support systems for use in other applications can also impair the accuracy of localization systems. For example, the localizing and tracking systems developed by Calypso Medical Technologies, Inc. can track tumors or other targets in a patient for surgical procedures, monitoring patients and diagnostic applications. Conventional patient support systems for these other applications can also impair the accuracy of the localization and tracking systems. Therefore, although conventional patient support systems for surgical procedures or other applications may be useful, they too are not well suited for use with localizing and tracking systems that use magnetic fields or other types of signals to track a target of a patient.